An organic EL display is generally formed by bonding together an organic EL element and a sealing substrate. In particular, a top-emission type organic EL display, which extracts light from the upper portion of an organic EL element, is formed by bonding to a substrate having red (R), green (G), and blue (B) color filters as a sealing substrate. A color conversion method is known as one means of obtaining an organic EL display capable of R, G, B multicolor light emission. A color conversion method is a method in which light emitted from an organic EL element is absorbed by a color conversion film arranged at the upper portion of the organic EL element, and light converted by the color conversion film passes through a color filter to reproduce a desired color.
An organic EL element generally has a structure in which are formed, in order on a substrate, a lower electrode, an organic EL layer, and an upper electrode. In order to form a plurality of emission portions which can be driven independently, each pixel of the lower electrode is insulated with a barrier wall, and active-matrix driving, connecting the lower electrodes of pixels with switching elements, can be performed. The organic EL layer includes at least an emission layer, and may include, as necessary, a hole injection layer, electron transport layer, and other layers.
An organic EL layer is extremely susceptible to oxygen and water, and when outside air or water intrudes into the panel interior and reaches the organic EL layer, growth of emission defect points called dark areas or dark spots occurs. Hence sealing films, comprising inorganic oxides, inorganic nitrides, or inorganic oxynitrides (SiO2, SiON, SiN, and similar), are formed so as to cover the structure of the upper electrode and below. In formation of a sealing film, generally a plasma CVD film deposition method is used. In a plasma CVD film deposition method, a gas mixture of monosilane, disilane, ammonia, nitrous oxide, hydrogen, nitrogen, and similar is introduced into the vacuum chamber into which the substrate for film deposition has been placed, and by inducing plasma discharge, a silicon nitride (SiNx), silicon oxynitride (SiON), silicon oxide (SiOx), or other film is deposited on the substrate for film deposition.
When a sealing film is for example formed from a SiNx single layer, it is necessary to form the sealing film to a film thickness of several μm, in order to provide a function to adequately block outside air and water. Hence due to the film deposition lead time required, and the effect of longer plasma discharge time, the substrate temperature rises, and there are concerns that the organic EL layer may be damaged as a result.
Further, it is known that because SiNx has large residual stress, cracks appear if SiNx film is formed to a film thickness of several μm. Hence in Patent Reference 1, formation of a multilayer-structure sealing film is proposed in which SiNx and, as a stress relaxation layer, SiON are layered, so that the residual stress of the SiNx film is relaxed and crack occurrence is prevented (see Patent Reference 1). Here, it is stated that the SiON film used as a stress relaxation layer must have a film thickness of from 2 to 10 times that of the SiNx film. However, in Patent Reference 1, there is no disclosure of the effectiveness of the multilayer structure for suppressing pinholes, which are a factor detracting from the sealing performance.
Further, Patent Reference 2 discloses, as a sealing film for a display device, a layered structure including a first layer of SiNx and a second layer of SiOx, SiON, or similar (Patent Reference 2). Here, it is stated that a third layer of SiNx may further be provided. In Patent Reference 2, it is stated that the second layer of SiOx, SiON or similar is effective in sealing pinholes in the first layer of SiNx, but it is not recognized that as the film thickness of the second layer (SiON or similar) increases, pinholes increase and the sealing film characteristics are degraded.    Patent Reference 1: Japanese Patent Application Laid-open No. 2006-164543    Patent Reference 2: Japanese Translation of PCT Application No. 2005-512299
Among organic EL elements, active-matrix driven organic EL elements have switching elements comprising TFTs or similar and wiring for such elements, and pixels are surrounded by barrier walls to separate lower electrodes, so that the upper surface has a shape with numerous depressions and protrusions. An upper surface with numerous depressions and protrusions is one cause of the occurrence of pinholes in the sealing film formed thereupon. For example, in the case of a sealing film formed from a SiNx single-layer film, even when the film thickness is increased to several w, it is difficult to completely suppress pinholes which have appeared. Further, formation of such a sealing film with large thickness poses the problem of damage to organic EL elements due to plasma discharge in the CVD method.